Method of compacting soap into sound bars



Dean 16, 1952 2,621,368

METHOD OF COMPACTING SOAP INTO SOUND BARS Filed Aug. 8, 1951 $050 Flo M; .Uana/dEMars/za/Z Patented Dec. 16, 1952 METHOD OF COMPACTING SOAP INTO SOUND BARS Donald E. Marshall, Edina, Minn., assignor to Micro Processing Equipment Inc., Des Plaines, 111., a corporation of Illinois Application August 8, 1951, Serial No. 240,928

9 Claims.

This invention relates to a method of compacting moldable particulated materials, such as milled soap granules, and has as its purpose to provide a commercially practicable method by which such material may be compacted into durable bars which are free of incipient cracks, which, when they occur, are caused by shearing along flow planes and air layers. In past attempts to compact such granular material these fractures developed when compacting pressure sufiicient to securely integrate the granules into a monolithic durable mass was exerted ina single compacting step.

The new technique of this invention is closely related to the inventions of the pending applications of Donald E. Marshall, Serial No. 129,093 filed November 23, 1949, now U. S. Patent No. 2,594,956, and Serial No. 177,268 filed August 2, 1950. Those applications respectively disclose compacting of non-aerated powders into form retaining aerated compacts through the use of buffer air and fluidized charges in the die chamber; and the continuous compacting of aerated 80 mesh sized granules in easy stages of churning compression in a worm and barrel type plodder prior to extrusion as a continuous rope-like blank for subsequent cutting and stamping into floating bars.

The present invention employs to some extent the entrapment of bufier-air which characterizes the invention of application Serial No. 129,093 combined with the progressive compacting feature of continuous integration as in Serial No. 177,268; however, in this invention progressive compaction is accomplished by repeatedly compacting the material between forming dies, the repeated impact of which integrates the granules into a monolithic durable mass Without churning the same; with the result that low-moisture soap granules having relatively poor compacting characteristics which, heretofore, could not be die cast without developing internal fractures can now be molded into well integrated bars either with suflicient air incorporated therein to make them float or with only 'sufficient air therein to improve their whiteness while leaving them dense enough to be non-floating.

The repeated striking of a bar soap blank by molding dies within a die box or shroud in itself is not new. This invention, however, introduces two important innovations in the die molding of powders: (1) sealing the shell or surface of the compact ineasy stages before'the full compacting pressure is applied to thereby effect the entrapment of finely divided air cells, both surrounding and within the soap granules, without developing air-layer cracks; and (2) integrating and securely knitting the particles together by repeatedly striking the compacted powder mass and releasing the pressure thereon between strikes, with the compacting pressure of successive strokes progressively increasing in carefully graduated increments. This progression of compacting pressures may be easily accomplished by forcing the stamping dies a trifle closer together on each succeeding strike. Very small increments of increased die closure, for instance & inch, will yield results not possible with larger increments. The number of strikes required to perfect the bar will depend upon the surface texture desired and the integrating characteristics of the soap granules being molded. At least three successive strikes are needed and since the surface polish improves as the number of strikes is increased, as many as ten strikes can be justified on soaps in the vitreous state if a glossy surface is desired.

The mass production of bars directly from powders has been long sought by the soap industry because of the many economies and variations in soap formulation it provides, but heretofore, certain insurmountable complications have militated against success when dealing with a soft and sticky material like soap. For example, if the granules were prepared with a moisture content sufficiently high to cold weld, such as the 12% to 14% moisture needed for roller milled soap which is continuously extruded, then the powder is so sticky that the stamping dies become fouled; and if granules of lower than 12% moisture were used the bars would crack when subjected to molding pressures high enough to Withstand the normal shocks to which a bar may be subjected.

Heretofore soap granules would not knit unless churned in a plodder worm to gain shear integration; or unless they were ultra-milled to gain integration by compacting without shear; and in some cases the granules required both aeration and ultra-milling. This invention with'its progressive compacting obviates all these troublesome requirements. With it powders drier than 12 may be used, as well as a very low initial compacting pressure to overcome the sticking of the soap compact to the dies; and then almost any degree of necessary durability can be built into the bar if the comp-acting pressure is increased in easy stages. Furthermore, the milling may be terminated short of that stage of fineness produced only by ultra-milling, while apin the aforesaid copending application, Serial No..

177,268, by grinding soap granules having less than 12% moisture until they pass through an 80 mesh screen, a fine textured bar may be integrated in a continuous worm and barrel extruder or plodder if done in easy stages of increasing pressure and assisted by the churning action of the worm which shears the particles into adhesion. According to the present invention these fine and dry soap powders, milled or unmilled, may be integrated by progressive compacting which tends to reproduce the shearing integration of the worm by the flowing action of the soap mass within the die chamber during each successive stage of compression and pressure release.

The aforesaid copending applications also teach that flaked soap or coarsely ground granules, 20 mesh for instance, if compacted at a moisture below 12% yield a bar with very coarse surface texture due to the individual granules being too large to blend into a monolithic mass free of mottle or coarse grain texture. And, if such powders are ground and screened to a finer mesh, the action of the dies develops cracks in the bar. when suificient'pressure is used to gain a durable mass because these fine powders do not knit as well as the coarser grained materialfrom which they were produced.

With the foregoing general statement of the invention in mind, reference is now made to the accompanying drawings which illustrate one manner of practicing the method of this invention according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a vertical cross sectional' view through a powder stamping die and die chamber with a charge of soap granules therein and ready to be compacted into a bar;

Figure 2 illustrates the die closed partially and I the mass partially compacted;

Figure 3 illustrates the die entirely closed and the soap mass fully compacted;

Figure 4 is a perspective view of a bar of soap produced by compacting granules according to the technique of this invention, and illustrating a preferred shape for the bar;

Figure 5 is a view in cross section and on an enlarged scale through one side portion of the dies and soap mass to illustrate their relative positions at the initial compacting stage;

Figure 6 is a view similar to Figure 5 but illustrating the dies retracted and the soap mass freed of compacting pressure after the first compression; and

Figure 7 illustrates the second compacting position of the dies which is advanced one increment beyond the initial compacting stage.

As in the aforesaid copending applications, the method of this invention involves the preparation of thesoap or other similar granules to be compacted. This may include dryinga high moisture p base such as one containin approximately 30% moisture, into flakes, chips, or granules containing 12% or less moisture. The d e p rial No. 129,942 filed Novemberll, 1949.

may be milled for texture improvement, then ground and screened into a molding powder either aerated or non-aerated during the milling operation Using a 40-ton Stokes Model 5-4 single die press, one adaptation of the invention is as follows:

The powder, produced as described, is charged into the die chamber 4 (Figure 1) and lower die 3 is positioned so that when the charge 5 is leveled off even with the tsp of the die chamber the proper weight of soap is measured by the cavity. Then die 2 is lowered into the die chamber and the mass given aninitial light compacting pressure as illustrated in Figure 2. Upon reopening the dies and raising the lower die 3 to the top of the die chamber 4, the partially formed bar may be removed and carefully examined for cracks by breaking it in two and noting the internal texture. If the bar will not'hold its shape the pres sure must be increased on the initial stroke by bringing the dies 2 and 3 closer together (approximately of an inch), being careful not to go so far as to crack its internal structure. The pressure thus empirically ascertained determines the initial molding position illustrated in Figure 5 wherein the dies are spaced the initial distance A.

The first pressure increment may be obtained by bringing dies 2 and 3 approximately 3 inch closer together at closure. This adjustment is made after the pressure is released and the dies are positioned'as illustrated in Figure 6 wherein the dies are spaced the distance C on release and the soapcompact has the dimension B.

The second stamping or strike is then made by bringing the dies. together to the lesser distance D, Figure 7, and the bar again examined for internal cracks. This routine constitutes one complete cycle of increased pressure and subsequent release.

This procedure is repeated three or more times choosing in each instance as the increment of increased die closure 2;? inch or inch. Normally four strikes will yield a finished bar; however, if an especially highly polished bar is desired, as many as ten progressive strikes may be justified, because each minute compression and expansion of the soap bar as the pressure is applied and released by the dies, tends to iron the surface of the. bar into a higher polish, particularly if the'soap has been milled to an ultramicrocrystalline texture by the hand milling technique described in the copending application, Se-

This ironing action ,is improved considerably if the die surfaces 6 are curved as required to produce the bar shape shown in Figure 4, since the curved formation facilitates tangential flow as contrasted with the perfectly rectangular surfaces of a brick-shaped bar.

When using aerated granules such as result from the band mill process of application Serial No. 129,942, these four to ten cycles of progressive compaction may still yield a floating bar due to retained aeration, but the surface will be polished as highly asa deaerated non-floating bar. By the same token a non-floating bar may still retain sufficientaeration to greatly improve the bar whiteness and have a highly polished surface.

An important advantage of this invention is that itenables the production of fine textured bars from very finely ground dry powder. For example, exceedingly fine textured floating or non-floating bars may be made from band milled powders which have been pulverized to 80 mesh, 100 mesh and finer before compacting by progressive stages using from three to ten stages to gain a monolithic bar and a, high surface polish.

To facilitate the preparation of these fine mesh powders it has been found that by first pulverizing the soap to the 80-100 mesh while the moisture content is below 7%, there is less likelihood of fouling the grinder and greater through-put per horsepower is obtained. This dry powder grinding may then be followed by the addition of moisture to bring the percentage of moisture above 9%. After the moisture content is thus raised the material is reground but only to about 20 mesh. This yields an excellent molding powder without the use of fine screens on the higher moisture material.

Synthetic detergents, tooth powders, shaving powders, shampoo powders, etc. such as described in the aforesaid copending application Serial No. 129,093 may be ground to an exceedingly fine dimension, 2 to 6 microns for instance, and still be compacted into aerated tablets by this technique and without the use of any more buffer air than is occluded in the loose powder as the charge is loaded into the die chamber. In such cases the compacting pressures are held much lower. Nevertheless, by repeatedly pressing the compact with each strike subjecting the same to slightly greater pressure a shell is developed which will retain both the shape and aeration. The final stroke then may be made at considerably higher compacting pressure than could otherwise be tolerated due to the slippery nature of exceedingly fine powders.

This general compacting technique may be practiced on many plastic or moldable materials other than detergents. Also it lends itself nicely to mass production. A turret type press may be used to gain high production of highly polished bars. In this case the cams which close and release the dies as the turret moves from one position to the next may be arranged so that each successive closure increases the compaction of the bar according to the progression of increments determined in the manner described. If ten stages are to be used then ten positions of the turret must be provided in addition to the loading and discharging positions. This makes possible a high production rate even though ten cycles of compression and release are used for each bar.

Though the preferred manner of developing the increments of increased compacting pressure is as has been described, i. e. by bringing the dies closer together on each strike, the increased pressure can also be developed by adding a small amount of soap granules or dust to the die chamber between each compression stroke and Without progressively diminishing the die spacing. Such a technique may be justified where a soap dust of special formulation is added to the outer surface of the bar to gain special color, lather, or polish effects; and, of course, can be combined with the progressive diminishing of the die spacing.

From the foregoing description it will be readily apparent to those skilled in soap making that this invention fills a long felt need in the art, and that while one complete adaptation of the invention has been described in detail it is understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the appended claims.

What I claim as my invention is:

1. A method of compacting powdered soap into bars which comprises: placing a measured quantity of the powdered soap in a die; subjecting the powdered soap in the die to an initial forming and shaping pressure empirically determined to form the same into a form and shape retaining compact free from cracks; subjecting the compact to a succession of intermittent applications of pressure with each pressure application slightly greater than the preceding one to thereby first seal the surface of the compact and as a result effect the entrapment of air therein; and releasing the compact of pressure between the intermittent pressure applications, said alternate applications and releases of pressure knitting the compact into a monolithic bar.

2. A method of compacting soap granules into sound bars, which comprises: mechanically subjecting a measured quantity of the granules to an initial degree compression empirically determined to form the same into a shape and form retaining compact free from cracks; sealing the surface of the compact and thus entrapping the air contained in the interstices of the compact by repeatedly subjecting the compact to a succession of applications of pressure with each application of pressure slightly greater than the preceding one and with the increments in compacting pressure sufficiently small to avoid fracturing the internal structure of the compact; and releasing the compacting pressure between pressure applications.

3. The method of compacting soap granules as set forth in claim 2 but wherein the soap granules are preliminarily processed to have a moisture content of less than 12%.

4. The method of compacting soap granules as set forth in claim 3 but wherein the less than 12% moisture granules are graded to a size smaller than 20 mesh.

5. The method of compacting soap granules as set forth in claim 2 but wherein the soap granules are first processed to occlude air therein and to give them a moisture content of less than 17%; and terminating the progressive compaction of the compact before the density of the resulting bar exceeds that of water so that the bar will float in water and have a highly polished deaerated surface layer.

6. The method of claim 5 but wherein the progressive compaction of the compact is continued until density of the resulting bar exceeds that of water so that the bar sinks in water but retains sufficient aeration below its deaerated surface layer to markedly whiten the bar.

7. A method of making a fine textured durable bar of soap having a highly polished surface, which comprises: compacting a measured quantity of soap granules containing less than 12% moisture and graded to a screen size smaller than 50 mesh into a bar of the desired size and shape by first subjecting the soap granules to an initial shaping and forming pressure empirically determined to form the same into a shape and form retaining compact free from cracks, and then subjecting the formed compact to a succession of small increments in compacting pressure with intervening releases of said pressure.

8. A method of compacting soap powders into durable bars having a highly polished surface, which comprises: refining a soap base by mechanical manipulation to less than 12% moisture content; pulverizing said refined soap to a screen size smaller than 50 mesh; subjecting the fine mesh powder within a die chamber to an initial forming pressure empirically determined to produce-a shape and form retaining compact free from cracks; and then subjecting the formed compact .in said die chamber to a succession of small increments in compacting pressure within a die chamber with intervening releases of said pressure.

9. The process of claim 8 but wherein said refined soap is pulverized at a moisture below the point which tends to foul the grinding operation followed by the addition of moisture to obtain a finished bar ranging in moisture between 7% and 11%, and subsequently grinding and screen- 15V 8 ing said higher moisture powder to a coarser grain size which will not foul the grinding operation preparatory to the successive compacting of the powder.

DONALD E. MARSHALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,210,924 Hood Aug. 13, 1940 $424,012. Bangham et al. July 15, 194? 

